Optimum Nozzle Angle of a Micro Solid-propellant Thruster

Abstract

The characteristics of supersonic flow field and thrust for a micronozzle used in a microthruster were analyzed numerically to determine the optimum nozzle geometry. Typical parameter values are 300 mu m throat diameter, 10 bar and 1000 K for stagnation conditions, and 1-100 ms for combustion completion. The effects of the boundary layer, heat loss, and unsteady stagnation conditions were considered. Thrust was much more dependent on the nozzle expansion angle than the area ratio or length. Optimum nozzle expansion angle for maximum thrust was close to 30 degrees for a planar 2D nozzle and 25 degrees for a 2D axisymmetric nozzle.